An understanding of the problem of inter-limb coordination in voluntary movements will be considerably advanced if the wiring diagram of long-spinal reflexes linking the cervical and lumbar enlargements is known in detail. Some gaps exist in our knowledge of such long-spinal reflexes, specifically involving 'dynamic gamma motoneurones' or 'static gamma motoneurones'. This proposal addresses itself to the problem of selective control of lumbar static and dynamic gamma motoneurones by afferents to the cervical segments of the spinal cord in the cat. There is considerable indirect evidence to support a role for dynamic fusimotor neurones for coordination of propriospinal mechanisms. The proposed experiments will test the hypothesis that the descending long-spinal reflexes, that originate from the dorsal neck and forelimb muscles, project excitation to lumbar dynamic gamma motoneurones and inhibition to the static gamma motoneurones. By studying the differences in such reflexes between animals with either pre-collicular or inter-collicular decerebration and by comparing them with high-spinal animals, the influence of spinobulbospinal reflexes will also be determined. In addition, the effects of such long-spinal pathways on the segmental reflexes of the alpha and gamma motoneurones will be determined. It is expected that these experiments will help in describing the spinal mechanism involved in the phenomenon of reflex reversal that is observed during a specific phase of locomotion.